JPH082427Y2 - Combustion chamber of direct injection diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a combustion chamber of a direct injection diesel engine, and more particularly, to the direction of reflection by injecting and injecting fuel injected from a fuel injection nozzle against the wall surface of the combustion chamber. The present invention relates to improvement of a combustion chamber of a type that forms and burns a good air-fuel mixture.

[Conventional technology]

The applicant has proposed in Japanese Patent Application No. 62-141450 a combustion chamber of a fuel injection, reflection type direct injection diesel engine. There, the combustion chamber is defined within a cavity formed in the top of the piston that opens upwards, the opening of the cavity projecting radially inward and the lower surface in a plane containing the piston axis. Is formed as a concave curved surface, and this concave curved surface serves as an injection fuel collision wall surface of the injected fuel from the fuel injection nozzle. Since the injected fuel collision wall surface is a concave curved surface, the fuel collision position changes up and down along the concave curved surface as the piston moves up and down, and the combustion reflection direction changes from near the outer peripheral edge of the combustion chamber to the combustion chamber center direction. However, the reflected fuel spray scans the combustion chamber over a wide range, and good mixture formation is possible.

[Problems to be solved by the invention]

However, the conventional combustion chamber structure is symmetric with respect to the entire axis of the combustion chamber axis, and the injected fuel collision wall surface acts in the same manner at low engine speed and high engine speed.

Therefore, during the cold idling operation, the amount of HC emission increases, and white smoke and a foul odor are generated. During cold idle operation, even if ignition occurs in the combustion chamber,
Since quenching is likely to occur due to cooling on the wall surface, it is desirable to burn as much as possible in the center of the combustion chamber. However, in the prior art, since the action of the fuel collision wall surface composed of the concave curved surface is invariable during any operation, naturally, during the cold idle operation, the reflected fuel spray is also generated near the wall surface of the outer peripheral edge portion of the combustion chamber. Has been supplied,
The above problem occurs.

Further, even when the engine speed is low, there are problems of increased HC emissions, white smoke, and deterioration of odor performance. This is because the swirl strength is low at low engine speeds, so the injected fuel flies to the fuel collision wall surface with a strong penetration force, and large particles of fuel particles wet the wall surface.

On the other hand, at high engine speed, conversely, the swirl strength is strong, the spray penetration force is insufficient, and a good mixture is not formed, so the black smoke emission characteristics deteriorate.

It is an object of the present invention to provide a combustion chamber structure that keeps the formation of an air-fuel mixture optimally by reflection on the wall surface when the engine speed is low and when the engine speed is high.

[Means for solving problems]

According to the present invention, the above object is achieved by the following combustion chamber of a direct injection diesel engine.

That is, (1) a combustion chamber of a direct injection diesel engine having an intake swirl, wherein the combustion chamber is defined in a cavity formed at the top of the piston and opening upward
At the opening of the cavity, a lip portion is formed which is formed inwardly in the radial direction and whose lower surface is formed as a concave curved surface opened downwardly of the piston in a plane including the piston axis. In the combustion chamber having an injected fuel collision wall surface that causes the injected fuel to collide with and be reflected, the injected fuel collides at high engine speed with the inclination angle of the first injected fuel collision wall surface portion at which the injected fuel collides at low engine speed. The inclination angle of the second injected fuel collision wall surface portion is
Differently from each other, the reflection direction of the collision fuel on the first injected fuel collision wall surface portion is directed toward the center of the cavity, and the reflection direction of the collision fuel on the second injection fuel collision wall surface portion is directed toward the cavity outer periphery. Combustion chamber of a direct injection diesel engine characterized by

More specifically, the combustion chamber of the direct injection diesel engine can take any one of the following aspects.

(2) Of the lower part of the lip part, the lower part of the lip part of the first injected fuel collision wall surface part is brought closer to the combustion chamber center side than the lower part of the lip part of the second injected fuel collision wall surface part.
A combustion chamber in which the angle of inclination of the wall surface portion of the injected fuel collision is set to be larger than the angle of inclination of the wall surface portion of the second injected fuel collision (corresponding to the first embodiment described later).

(3) The inclination angle of the first injected fuel collision wall surface portion is set by making the upper portion of the lip portion of the first injected fuel collision wall surface portion of the upper portion of the lip portion farther from the center of the combustion chamber than the other lip portion upper portions. Is set at an angle greater than the inclination angle of the second injected fuel collision wall surface portion, and a turbulent flow generation concave portion is formed near the fuel injection nozzle side of the first injected fuel collision wall surface portion (see the second embodiment described later). Correspondence).

(4) The first injected fuel collision wall surface portion is inclined with respect to the second injected fuel collision wall surface portion and is kept away from the fuel injection nozzle, and the first injected fuel collision wall surface portion is disturbed near the fuel injection nozzle side. A combustion chamber in which a flow generating recess is formed (corresponding to a third embodiment described later).

[Action]

In the combustion chamber of (1) above, the collision fuel reflection direction at the first injected fuel collision wall surface portion is directed toward the cavity center,
Since the collision fuel reflected on the wall surface of the second injected fuel collision is directed toward the outer periphery of the cavity, quenching at low engine speed is prevented, HC emissions are reduced, white smoke and odor are reduced, and high At the time of rotation, the output is improved by mixing with a large amount of air.

More specifically, in the case of (2) above, since the inclination of the first injected fuel collision wall surface portion is higher, the reflected fuel at the first injected fuel collision wall surface portion is the second injected fuel collision wall portion. Compared to the reflected fuel on the wall surface, the reflected fuel is more toward the center of the combustion chamber and the reflected fuel is not supplied to the vicinity of the outer peripheral edge of the combustion chamber when the engine is running at low speed. Therefore, during cold idling, HC emissions are reduced, and white smoke and odor are also reduced.

If the structure of (3) above is adopted, in addition to the same effect as (2) above when the engine is running at low speed, the swirl flow separates from the wall surface on the upstream side, so that the swirl flow enters the recess near the wall surface of the first injected fuel collision. A minute turbulent flow is formed, which weakens the strong injected fuel penetration force at low rotation speed, suppresses the wetting of the first injected fuel collision wall surface portion, and promotes the action of reducing HC emissions, white smoke, and odor.

According to the structure of (4), since the distance between the first injected fuel collision wall surface portion and the fuel injection nozzle is larger than the distance between the second injected fuel collision wall surface portion and the fuel injection nozzle, flight injection is performed. The penetration force of the fuel is weakened by the swirl and weakened by the minute turbulent flow in the concave portion in the immediate vicinity of the first injected fuel collision wall surface portion, and the adhesion of fuel to the first injected fuel collision wall surface portion is reduced. HC emissions, white smoke, and odors are reduced at low speeds.

〔Example〕

Hereinafter, three preferred embodiments of the combustion chamber of the direct injection type diesel engine of the present invention will be described with reference to the drawings.
1 to 5 show the first embodiment, FIGS. 6 to 10 show the second embodiment, and FIGS. 11 to 14 show the third embodiment. Throughout the figures, common members are numbered the same.

First, a configuration common to each embodiment will be described with reference to FIGS. 1 to 5, for example.

1 and 2, reference numeral 10 denotes a combustion chamber of a direct injection diesel engine having an intake swirl. Combustion chamber 10
Is enclosed in a cavity 14 formed at the top of the piston 12 and opening upward. An annular lip portion 16 that protrudes inward in the radial direction is formed at the opening of the cavity 14, and the lower surface of the lip portion 16 is formed into a concave curved surface that opens downwardly of the piston within a plane including the piston axis. The injected fuel collision wall surface 18 is formed. The fuel injection nozzle 20 is fixedly provided on the cylinder head above the center of the combustion chamber, and has at least one fuel injection port. The injection fuel 22 injected through the fuel injection nozzle 20 has a piston 12 at a top dead center or a top dead center. When it is near the point, it collides with the injected fuel collision wall surface 18. The deep portion 24 of the cavity 14 is formed by being further scooped outward in the radial direction from the injected fuel collision wall surface 18. The bottom surface of the cavity 14 is a flat surface.

The injected fuel collision wall surface 18 is composed of a concave curved surface opened below the piston, and as the piston 12 rises, the reflected direction of the injected fuel 22 changes from 22a to 22b in FIGS. 3 and 4,
It is formed into a curved surface shape that scans a wide range from the outer peripheral side toward the center of the combustion chamber in the longitudinal sectional direction. Also, the flight direction of the injected fuel 22 is deflected in the cross-sectional direction in the swirl direction due to the presence of the swirl 26, as shown in FIGS. 1 and 5. At low engine speed, the swirl 26 is weak because the amount of intake air is small, and when the engine is running at low speed, the amount of deflection of the injected fuel 22L is small and goes straight. Since the intake amount is large and the swirl 22 is strong at high engine speed, the amount of deflection of the injected fuel 22H at high engine speed is large. The portion of the injected fuel collision wall surface 18 where the injected fuel 22L collides and is reflected at low speed is defined as the first injected fuel collision wall surface portion 18L, and the portion where the injected fuel 22H at high speed is impinged and reflected. Is defined as the second injected fuel collision wall surface portion 18H. First injection fuel collision wall surface part 18L
And the second injected fuel collision wall surface portion 18H are formed so that their inclination angles are different from each other. Previously this was the same as each other. Further, specifically, the reflection direction of the collision fuel at the first injected fuel collision wall surface portion 18L is directed toward the cavity center, and the reflection direction of the collision fuel at the second injected fuel collision wall surface portion 18H is It is directed toward the outer periphery of the cavity.

 Next, a configuration unique to each embodiment of the present invention will be described.

In the first embodiment of the present invention, as shown in FIGS. 1 and 2, of the lower portion of the lip portion 16, the lower portion of the lip portion of the first injected fuel collision wall surface portion 18L is subjected to the second injected fuel collision. The wall portion 18H is located closer to the center of the combustion chamber than the lower portion of the lip portion, and the inner diameter of the upper portion of the lip is the same in the circumferential direction. As a result, the inclination angle of the first injected fuel collision wall surface portion 18L is relatively high, and the inclination angle of the second injected fuel collision wall surface portion 18H is relatively high. In other words, the injected fuel collision wall surface
The narrow angle α between 18 and the injected fuel 22 is larger in the first injected fuel collision wall surface portion 18L than in the second injected fuel collision wall surface portion 18H. Therefore, the injected fuel collision wall surface 18 and the cavity deep
The corner portion 30 where the upper wall surface of 24 intersects is
The corrugations in the circumferential direction project inward from the other portions of the first injected fuel collision wall surface portion 18L. The first injection collision wall surface portion 18L and the second injection fuel collision wall surface portion 18H are curved in the circumferential direction and are connected smoothly.

In the second embodiment of the present invention, as shown in FIG. 6 and FIG. 7, among the upper portions of the lip portion 16, the upper portion of the lip portion of the first injected fuel collision wall surface portion 18L is located above the other lip portions. Is also away from the center of the combustion chamber. Injection fuel collision wall surface 18
And the corner 30 where the cavity deep part 24 intersects the upper wall surface is
As shown in FIG. 10 and FIG. 10, the diameter is constant in the circumferential direction.
As a result, the inclination of the first injection collision wall surface portion 18L becomes the second
Stand up from the slope of the injected fuel collision wall surface portion 18H. Lip part 1
The inner peripheral surface of the upper portion of 6 is corrugated in the circumferential direction, and is recessed toward the outer peripheral side in the first injected fuel collision wall surface portion 18L. by this,
A concave portion 28 is formed in the first injected fuel collision wall surface portion 18L in the immediate vicinity of the fuel injection nozzle, and when the swirl 26 flows into the concave portion 28 away from the upstream lip portion inner peripheral wall surface, a minute turbulent flow of separation, so-called A microturbulence is formed inside the recess 28.

In the third embodiment of the present invention, as shown in FIGS. 11 and 12, the first injected fuel collision wall surface portion 18L is inclined more than the second injected fuel collision wall surface portion 18H and the fuel injection is performed. Keep away from nozzle 20. As a result, the lip 16
A concave portion 28 for generating a minute turbulent flow, which is similar to that of the second embodiment, is formed on the inner periphery of the first injection fuel collision wall surface portion 18L in the immediate vicinity of the fuel injection nozzle side.

 Next, the operation of the present invention will be described.

First, the operation common to each embodiment will be described. When the piston 12 moves up near the top dead center, fuel is injected from the fuel injection nozzle 20, and the injected fuel 22 flies in the combustion chamber 10 in which the intake swirl 26 is swirling and collides with the injected fuel. It collides with the wall surface 18 and is reflected. Swirl 26 at low engine speed
Is weak, the injected fuel 22 travels almost straight, and at high engine speed, the swirl 26 is strong and is deflected toward the swirl 26.
Therefore, the positions of the first injected fuel collision wall surface portion 18L with which the injected fuel 22 collides at low speed and the second injected fuel collision wall surface portion 18H with which the injected fuel 22 collides at high speed are displaced in the swirl direction. . By making the structures of the first injected fuel collision wall surface portion 18L and the second injected fuel collision wall surface portion 18H different from each other, the collision characteristics and the reflection characteristics change at low engine speed and high engine speed. Further, specifically, since the reflection direction of the collision fuel on the first injected fuel collision wall surface portion 18L is directed toward the cavity center, the fuel is still sufficiently warm at low engine speed, especially during cold idle operation. Prevents incomplete combustion by touching the outer peripheral wall surface of the cavity, reducing HC emissions, white smoke, and odor. Further, since the reflection direction of the collision fuel at the second injected fuel collision wall surface portion 18H is directed toward the outer periphery of the cavity, the fuel is sufficiently in the outer periphery of the cavity when the engine is running at low speed (the outer wall surface of the cavity is sufficiently warm). It is mixed with various air and completely burned, improving the engine output.

Next, the operation peculiar to each embodiment of the present invention will be described.

In the first embodiment of the present invention, since the first injected fuel collision wall surface portion 18L is sloping, the injected fuel 22 injected at the time of low engine speed, as shown in FIG. Although it is reflected in a scanning manner due to movement, it is reflected relatively toward the center of the piston. For this reason, when the engine is running at low speed, the reflected fuel is not supplied to the outer peripheral edge portion of the cavity deep portion 24 in the immediate vicinity or is reduced. Therefore, the amount of HC emission, white smoke, and bad odor during the cold idle operation, which is included when the engine speed is low, are significantly reduced.
At high engine speed, as shown in Fig. 4, injected fuel
22 is reflected by the relatively injured second injected fuel collision wall surface portion 18H, scans the inside of the combustion chamber 10 over a wide range, and good combustion as in the conventional case can be obtained.

In the second embodiment of the present invention, when the engine speed is low, the injected fuel 22 collides with the relatively high first injected fuel collision wall surface portion 18L and is reflected toward the piston center side as shown in FIG. To be done. In addition, the injected fuel is
As shown in FIG. 9, 22 collides with the relatively injured second injected fuel collision wall surface portion 18H and scans the combustion chamber 10 over a wide range. Therefore, there is an effect similar to that of the first embodiment. In addition to this, in the second embodiment, when the first injected fuel collision wall surface portion 18L is stood upright, the upper portion of the lip portion is retracted outward in the radial direction. A recess 28 is formed in the immediate vicinity of the portion 18L. As a result, the swirl 26 flowing along the inner peripheral surface of the lip portion 16 on the upstream side of the recess 28 generates a minute turbulent flow in the recess 28. The injected fuel 22 flying from the fuel injection nozzle 20 toward the first injected fuel collision wall surface portion 18L at the time of low engine speed is disturbed by the minute turbulence when it reaches the recess 28, and the amount of adhesion to the wall surface is reduced. To do. Further, due to the presence of the concave portion 28, the first injected fuel collision wall surface portion 18L becomes the second injected fuel collision wall surface portion 1L.
Since the fuel is injected farther from the fuel injection nozzle 20 than 8H, the penetrating force of the injected fuel 22 is weakened during the flight, which also reduces the amount of fuel adhered to the first injected fuel collision wall surface portion 18L. As a result of these, the fuel adhesion to the first injected fuel collision wall surface portion 18L is reduced, and H
C emission is reduced, and white smoke and odor are also reduced. At high engine speed, good combustion can be obtained as in the first embodiment.

In the third embodiment of the present invention, the first injected fuel collision wall surface portion 18L is inclined more than the second injected fuel collision wall surface portion 18H and is further away from the fuel injection nozzle 20. In addition to the same effect as that of the first embodiment, the flight distance of the injected fuel 22 flying from the fuel injection nozzle 20 to the first injected fuel collision wall surface portion 18L becomes large at low engine speed, the penetration force is reduced, and the recessed portion is reduced. It is also disturbed by the minute turbulent flow of 28, thus reducing the amount of fuel adhering to the first injected fuel collision wall surface portion 18L. Therefore, HC emissions at low engine speeds are reduced, and white smoke and odor are also reduced. At high engine speed, good combustion can be obtained as in the first embodiment.

[Effect of device]

According to the present invention, HC emission, white smoke, and bad odor are reduced at low engine speeds, including during cold idle operation, and good combustion is maintained at high engine speeds.

[Brief description of drawings]

1 is a plan view of a combustion chamber of a direct injection diesel engine according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is combustion of FIG. 4 is a half sectional view of the combustion chamber at low engine speed, FIG. 4 is a half sectional view of the combustion chamber of FIG. 2 at high engine speed, and FIG. 5 is a deflection diagram of fuel injected by the swirl in FIG. 1; Is a plan view of a combustion chamber of a direct injection diesel engine according to a second embodiment of the present invention, FIG. 7 is a sectional view taken along line VII-VII of FIG. 6, and FIG. 8 is an engine of the combustion chamber of FIG. Fig. 9 is a half sectional view at low speed, Fig. 9 is a half sectional view at high engine speed in the combustion chamber of Fig. 7, Fig. 10 is a deflection diagram of injected fuel by swirl in Fig. 6, and Fig. 11 is the present invention. FIG. 12 is a plan view of the combustion chamber of the direct injection diesel engine according to the third embodiment of the present invention, and FIG. 12 is a line XII-XII in FIG. Sectional view taken along, Fig. 13 half-sectional view at the time of low engine speed of the combustion chamber of Fig. 12, Fig. 14 is a deflection diagram of the injected fuel due to the swirl in Figure 11. 10 …… Combustion chamber 12 …… Piston 14 …… Cavity 16 …… Lip portion 18 …… Injection fuel collision wall surface 18L …… First injection fuel collision wall surface portion 18H …… Second injection fuel collision wall surface portion 20 …… Fuel injection nozzle 22 …… Injected fuel 28 …… Concave

Claims (1)

[Scope of utility model registration request] 1. A combustion chamber of a direct-injection diesel engine having an intake swirl, the combustion chamber being defined by an upwardly-opening cavity formed at the top of the piston, and the opening of the cavity being defined by the cavity. Is a lip portion that is formed in a concave curved surface that projects inward in the radial direction and the lower surface opens downwardly of the piston in a plane including the piston axis, and the concave curved surface is collided with the fuel injected from the fuel injection nozzle, A combustion chamber having a reflected injection fuel collision wall surface, and a second injection fuel collision in which the injection fuel collides at the time of high engine speed, and the inclination angle of the first injection fuel collision wall surface portion at which the injected fuel collides at low engine speed The inclination angle of the wall surface portion is different from each other, and the reflection direction of the collision fuel on the first injected fuel collision wall surface portion is directed toward the center of the cavity,
A combustion chamber of a direct injection diesel engine, characterized in that the direction of reflection of the impinging fuel on the wall surface of the impinging fuel colliding with is directed toward the outer periphery of the cavity.